1. Field of the Invention
This invention relates to a blood plasma-separating membrane and a blood plasma separator using the membrane. More particularly, it relates to a blood plasma-separating membrane to be used in the therapy of blood plasma replacement or for the collection of blood plasma from a donor or from a blood bag and to a method for blood plasma separation which obviates the necessity for priming.
2. Description of the Prior Art
The method of blood plasma separation for separating the blood into the blood cell component and the blood plasma component is used for numerous medical purposes such as, for example, the blood plasma replacement which comprises isolating blood plasma from the blood of a patient who has the cause for disease in the blood plasma component and discarding the isolated blood plasma or replacing it with the blood plasma from a normal healthy person, the blood plasma collection which comprises collecting the blood plasma from the blood of a normal healthy person, and the blood plasma separation rom the preserved blood which comprises separating the preserved blood into the blood cell component and the blood plasma component.
Generally, the method of separation with a membrane is advantageous over the method of centrifugal separation in respect that the apparatus is inexpensive and the operation of separation suffers from no leakage of the blood cell component into the separated blood plasma component. It requires the membrane type blood plasma separator, preparatory to use, to be filled with a large amount of physiological isotonic liquid so as to purge the interior of the device and expel bubbles from the device. This preparatory treatment is called a "priming." This operation, therefore, constitutes itself a drawback from the economical and procedural points of view. Further, since the collected blood plasma is destined to be diluted with the physiological isotonic liquid, this method has another disadvantage that the blood plasma collected at all is not fully satisfactory in quality. The method of separation using the membrane, therefore, is desired to obviate the necessity for giving the separating device such purging and priming treatments as with a physiological isotonic liquid preparatory to use.
When the membrane for separating blood components is made of a hydrophobic material, it allows no passage therethrough of blood plasma rom the introduced blood only unless water is present in the pores of the membrane. In contrast, the membrane made of a hydrophilic material, as described in JP-A-62-290,469(1987), allows safe passage of blood plasma therethrough and yet has the disadvantage that it causes hemolysis during the introduction of blood. Specifically, when the priming treatment of the separator is omitted and the blood is brought into direct contact with the porous membrane in a dry state, since capillarity is initiated instantaneously on the surface of the porous membrane and the blood plasma component is suddenly absorbed in the interior of the porous membrane and then passed externally through the porous membrane, the red blood cells which are incapable of passing through the pores in the membrane are dissolved on the surface of the membrane. Hence the phenomenon of hemolysis entailing liberation of hemoglobin. This phenomenon of hemolysis not only impairs the quality of the collected blood plasma but also jeopardizes the safety of the patient or the donor.
As means to avoid the degradation of the quality of the collected blood plasma in consequence of this phenomenon of hemolysis or due to the use of physiological isotonic liquid for the priming treatment, a membrane type blood plasma separator and a blood component collecting set have been proposed by JP-A-62-290,469(1987) and JP-A-63-226,364(1988). The blood plasma separator, however, is finished by a procedure which comprises causing the interior of the separator to be filled with physiological isotonic liquid and then expelling the charged liquid out of the separator interior with compressed air. It, therefore, has as a problem the complication of process of manufacture and entails the disadvantage that the physiological isotonic liquid inevitably suffered to remain inside the pores demands due consideration as to preservation of quality, deterioration by aging, and safety.
An object of the present invention, therefore, is to provide a novel blood plasma-separating membrane, a blood plasma separating-membrane unit, a blood plasma separator, and a method for blood plasma separation.
Another object of this invention is to provide a blood plasma-separating membrane, a blood plasma-separating membrane unit, a blood plasma separator, and a method for blood plasma separation, which obviate the necessity for a complicated priming treatment with a physiological isotonic liquid preparatory to use, avoid inducing the phenomenon of hemolysis even when the blood is directly introduced thereto for the isolation of blood plasma, and exclude the otherwise possible dilution of the separated blood plasma with the physiological isotonic liquid.